Make double buffering optional; if it is really wanted locking should be used.
* Remove the BR24 specific radar log (windows); there were various remnants which were nice in development (before my time)
  but they cause problems (see http://osdir.com/ml/wx-users/2010-10/msg00182.html) when closing the application, and logging
  to opencpn.log is much more convenient once users start working with it instead of developers.

* Change the receiving thread from detached to joinable -- which is the correct paradigm in this instance.

* Various cleanup